HEM’s Last Visitor: HDAs

I knew before I started the project that the He Art Museum would be the backdrop for the plant animation. As I continued to piece things together, this idea kept creeping in about how these large public spaces would change if we weren’t around. I decided that my plant would be one of the last to visit the museum. After completing the structure, I set out to create a few tools to quickly “dress” every surface with a happy little visitor. In this brief breakdown, I’ll walk you through a few of the tools I created to speed things along.

Ivy Scattering

The scene uses four instances of the same ivy scatter HDA. The available parameters are simple as I either wanted ivy hanging from walls or under the stairs. The main points are an easy-to-understand density parameter, size and rotation control, the all-important seed, and a toggle to populate inside faces. This last parameter is a group based on normals facing the origin.

Fern/Leaf Scattering

Ferns and leaves were scattered using the same tool. It's essentially the ivy scatter HDA but with a couple of extra parameters. This tool was meant to scatter on both the main floor and staircases. It has a scatter exclusion scale, so I didn't have any clipping into the main plant, and a drop-down menu for selecting an area to scatter on. The incoming meshes from Unreal are separated based on normal orientation and scatter location is selected after that. The larger leaf meshes were made in Houdini by scattering handmade leaves on a grid, which I think is by far the easiest way to get an optimized result. The leaves were cut from a Quixel atlas in Blender.

Vine Generation

There were two separate HDAs for creating all the vines. One had additional inputs for collision objects and the other for scattering on the final mesh. A main curve was placed in Unreal and this was wrapped with additional curves. All of those were run through a vellum solver using hair constraints. These were either pinned at the ends or allowed to completely fall onto the colliders. Both versions of this HDA had post-smoothing and curve radius controls, as well as a material instance slot, for which I used a light-colored bark from Quixel.

Bonus: Materials Overview

This wasn't enough to warrant its own blog post, but I used Megascans as a jumping-off point for the structural pieces. Additional height information was required for the concrete walls and noise/grunge breakup for the whole kit. I like to give myself lots of control in the material instance and convert to constants later if needed. A couple of noise textures used throughout the project control blending between material attributes for the moss, puddles, and dry concrete. These same noise patterns are altered with cheap contrast or simply adding/subtracting small values to get the desired effect for the stairs and walls.

If you have any questions or comments, don't hesitate to reach out. My contact information is linked on the left and at the bottom. 'Til next time!